1. Field of the Present Invention
This invention relates to an evaporation installation of the type generally used for the evaporation of materials on substrates. More particularly, the invention relates to depositions of metallic compounds on integrated circuits which are being manufactured from silicon wafers, although other types of substrates may be utilized.
2. Discussion of the Related Art
FIG. 1 schematically shows a conventional evaporation installation. Such an installation is formed by a vacuum chamber 1 within which three supports S1, S2 and S3 are arranged. Each bell-shaped support is formed by a concave surface, having a generally circular circumference, and includes a plurality of openings 2 for receiving the silicon wafers, the surfaces to be processed being directed towards the inside (the concavity) of the supports. In FIG. 1, only a few openings 2 of support S1 have been shown, but all supports include openings along their entire surface.
Each support S1, S2 and S3 is rotatably mounted on a shaft, respectively A1, A2, A3, perpendicular to its surface at its top. Shafts A1, A2, A3 are supported by a common suspension frame 3, which is itself rotatably mounted on a vertical main shaft 4 which is supported by an upper wall 5 of chamber 1. Frame 3 also supports arms P1, P2 and P3 at the free ends on which shafts A1, A2 and A3 are located. The rotating motion of frame 3 transmits, generally through bevel gears (not shown), a rotating motion to transmission shafts (not shown) contained in arms P1, P2, and P3 which transmit the rotating motion, by similar means, to shafts A1, A2 and A3. Supports S1, S2 and S3 are generally called "planet members" due to their eccentric respective motions. The internal surfaces of the supports are turned towards an evaporation source 6.
FIG. 2 is a developed view which shows the three supports S1, S2 and S3 in the same plane, each support being shown in a plane perpendicular to its axis of rotation. As shown by this drawing, supports S1, S2 and S3 are all rotated in the same direction. The rotating motions are indicated in FIGS. 1 and 2 by an arrow F1 for the rotation of frame 3 and by arrows F2 for the rotation of each support S1, S2 or S3 around their corresponding shafts A1, A2 or A3.
An evaporation cycle consists of loading chamber 1 with supports S1, S2 and S3 which support the wafers to be processed, performing a vacuum pumping of the inside of chamber 1, heating the internal space of chamber 1, energizing evaporation source 6 in order to cause a deposition, cooling down and ventilating the chamber, and extracting the supports. The rotating motions, transmitted to frame 3 and to supports S1, S2 and S3, ensure a uniform deposition on the surfaces to be processed. The operation of such an installation is known.
A problem which appears in this type of installation is linked with the duration of the evaporation cycle. In practice, for a conventional installation with three supports having a diameter of around one meter, a cycle has a duration of several hours from the loading to the unloading of chamber 1. The efficiency of such an installation, which is defined as the duration of a cycle for one wafer, is thus generally mediocre.